This invention relates generally to gas turbine engines, and more specifically to rotor blades used with gas turbine engine combustors.
A gas turbine engine typically includes a core engine having, in serial flow arrangement, a high pressure compressor which compresses airflow entering the engine, a combustor which bums a mixture of fuel and air, and a turbine which includes a plurality of rotor blades that extract rotational energy from airflow exiting the combustor. the burned mixture. Because the turbine is subjected to high temperature airflow exiting the combustor, turbine components are cooled to reduce thermal stresses that may be induced by the high temperature airflow.
The rotating blades include hollow airfoils that are supplied cooling air through cooling circuits. The airfoils include a cooling cavity bounded by sidewalls that define the cooling cavity. To maintain structural integrity of the airfoil, the sidewalls are fabricated to have a thickness of at least 0.168 inches. The cooling cavity is partitioned into cooling chambers that define flow paths for directing the cooling air.
During rotor blade manufacture, a plurality of openings are formed along a trailing edge of the airfoil for discharging cooling air from the airfoil cavity. More specifically, an electro-chemical manufacturing (EDM) process is used to extend the openings from the airfoil trailing edge into the airfoil cavity. As the cooling openings are formed with an EDM electrode, the thickness of the sidewalls may permit the electrode to inadvertently gouge the sidewall causing an undesirable condition known as trailing edge scarfing. Depending on the severity of the scarfing, the structural integrity of the airfoil may be compromised, and the airfoil may need replacing. Furthermore, operation of an airfoil including scarfing, may weaken the airfoil reducing a useful life of the rotor blade.
In an exemplary embodiment, a gas turbine engine includes rotor blades including an airfoil that facilitates reducing manufacturing losses due to airfoil trailing edge scarfing. Each airfoil includes a first and second sidewall connected at a leading edge and a trailing edge. The sidewalls define a cooling cavity that includes at least a leading edge chamber bounded by the sidewalls and the airfoil leading edge, and a trailing edge chamber bounded by sidewalls and the airfoil trailing edge. The cooling cavity trailing edge chamber includes a tip region, a throat, and a passageway region connected in flow communication such that the throat is between the tip region and the passageway region. Furthermore, the tip region is bounded by the airfoil tip and extends divergently from the throat, such that a width of the tip region is greater than a width of the throat.
During an airfoil manufacturing process, an electro-chemical machining (EDM) process is used to form cooling openings that extend between the airfoil trailing edge and the cooling cavity trailing edge chamber. During the EDM process, the reduced thickness of the trailing edge chamber tip region facilitates reducing inadvertent gouging of the airfoil, thus preventing scarfing of the airfoil. As a result, manufacturing losses due to trailing edge scarfing are facilitated to be reduced in a cost-effective and reliable manner.